using System;

public delegate void LogHandler(string s);

public class Process {
    public event LogHandler LogEvent = null;

    public void Run() {
        if (LogEvent != null)
            LogEvent("Start process");

        //...

        if (LogEvent != null)
            LogEvent("Stop process");
    }
}

public class Tracer {
    public void Trace(string s) {
        System.Console.WriteLine("Tracer: {0}", s);
    }
}

public class Test {
    public static void Log(string s) {
        System.Console.WriteLine("static Log: {0}", s);
    }

    public static int Main(string[] args) {
        Process p = new Process();
        Tracer t = new Tracer();

        //... LogHandler lh = null;
        //... lh += new LogHandler(Log);
        //... lh += new LogHandler(t.Trace);
        //... p.LogEvent += lh;

        p.LogEvent += new LogHandler(Log);
        p.LogEvent += new LogHandler(t.Trace);
        p.Run();
        return 0;
    }
}